Dry Sump Oil System - Suck It!

Although the hosts of "Top Gear" America can somehow get away with it, in most situations, sucking it up isn’t something you want to do. However, on-track beat-downs don’t qualify as most situations, and in racing environments, an oiling system that sucks incessantly is exactly what an engine needs. Enter dry sump lubrication. Just about every race car on the planet — whether it’s in NASCAR Sprint Cup, NHRA Pro Stock, or Formula One — relies on a dry sump oil system. Even those goofball drifters have them. Whether the performance machine at hand dishes out g-forces under braking, acceleration, cornering, or all three, the laws of physics do their best to uncover the pump pickup and leave it gurgling on aerated froth instead of drinking a steady supply of oil. As all five generations of Camaros continue to accelerate harder with ever-increasing horsepower totals, and corner more briskly thanks to cutting-edge suspension technology and modern tire compounds, ever-greater demands are placed upon the oiling system. It just so happens that many of today’s most capable Camaros boast LS small-block power, and as such, it only makes sense to explore what’s involved with fitting a dry sump oiling system on these motors.

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Not long ago, converting a wet sump motor over to dry sump lubrication required piecing together dozens of different parts out of a catalog. This process is hardly rocket science, but it does increase the potential for messing something up, and at the very least, it can be a major pain. Fortunately, companies like Armstrong Race Engineering (ARE) make things easy. It offers a full catalog of bolt-in dry sump systems for import and domestic engines, including several different options for LS-series small-blocks. To get a first-hand look at what it takes to fit a dry sump oiling system onto a Gen III small-block, we dropped by HK Enterprises in Houston, Texas.

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At any given time, HKE has more than two dozen LS small-blocks — ranging from street/strip to full race — under construction, and the shop has earned a reputation in the Gen III/IV community for building incredibly potent yet extremely reliable engine combos. HKE just so happened to be installing a dry sump setup on a 1,250hp 408ci drag motor during our visit, so we were eager to check it out. While the process of installing a dry sump setup is somewhat universal, there are several application-specific quirks that need to be addressed when the engine platform at hand is the LS-series small-block. That said, upgrading to a dry sump system is a big-time financial commitment that can easily top $3,000. As such, it’s worthwhile to take a comprehensive look at how they work, and the dividends they can yield in both oil control and horsepower before delving into the installation process.

Dry Sump Basics

In a typical wet sump oiling system, an internally mounted pump pulls oil out of the pan through a pickup tube. Pressurized oil is then routed through the main galley in the block en route to the oil filter. The oil then travels up the back of the block to the main feed galley, which runs through the lifter bores. From there, oil trickles down to the mains to lubricate the crank, rods, and main and rod bearing. Just like the Gen I small-block, LS-series engines direct oil to the cylinder heads through holes drilled into the lifters and pushrods. This lubricates and cools the valvesprings and rocker arms, and the oil then drains back into the pan through passages in the cylinder heads and block. Of course, this entire chain of events assumes that the oil pump pickup remains submerged in oil all the time. Anytime oil pushes up against the sides of the pan instead of going through the pickup tube, this entire sequence is disrupted, and catastrophic engine failure looms just around the corner.

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On the other hand, in a dry sump oiling system, the pan itself contains almost no oil at all. It functions more as a drip pan than a traditional oil pan. As such, a mixture of oil and air is scavenged from the oil pan through rubber or steel braided hoses by an externally mounted pump, which is belt-driven by the crankshaft. The oil is then directed into the top of an external supply tank typically mounted in the engine compartment. As oil scavenged out of the pan trickles down the supply tank, internal baffles separate the air from the oil. The oil pump then draws oil from the outlet at the bottom of the supply tank, and sends pressurized oil back into the block. Unlike in a wet sump oiling system, a dry sump pump is really two pumps in one, as it both sucks oil out of the pan and sends pressurized oil back into the block’s oil galleys.

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One of the great advantages of a dry sump system is that it can be set up in multiple stages depending on the requirements of a specific application. A stage refers to how many scavenge and pressure circuits a dry sump pump has, and anywhere from one to six stages is common. For instance, in a typical four-stage dry sump system, there are three scavenge pickup points in the oil pan in addition to the pressure stage on the pump. Additional pickup points allow scavenging oil more evenly off of multiple areas of the motor. In a multi-stage dry sump system, for example, oil can be scavenged from the front and back of the motor, as well as the lifter valley.

Horsepower Advantage

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Storing oil in a separate auxiliary oil tank instead of the pan yields several obvious advantages. First off, it ensures that the pump will always have a steady supply of oil regardless of the g-forces at work, and the result is rock solid oil pressure. Secondly, a dry sump system’s oil supply tank can hold anywhere between 4 and 20 quarts of oil. The increased capacity cools oil temperatures and further stabilizes pressure, which is usually adjustable from 40 to 60 psi using an external regulator. Furthermore, since dry sump pans do not store any oil, they are very low profile in design. This allows lowering an engine farther down into the chassis for improved handling and braking.

Although dry sump systems were originally designed for improved oil control, they can yield dividends in horsepower as well. In a wet sump system, the crankshaft counterweights and rods must whip through the oil, and the resulting increase in windage and drag reduces horsepower output. Conversely, with no oil to contend with in a dry sump pan, windage is virtually eliminated. Likewise, in addition to scavenging oil out of the pan, a dry sump pump can function as a vacuum pump as well. This ensures that there is less pressure inside the crankcase than above the pistons, which improves ring seal, reduces blow-by, and increases horsepower. Negative crankcase pressure also allows the rotating assembly to accelerate more quickly, as there is less resistance acting upon the pistons as they travel down the cylinder bores. The affect is similar to having a lightweight rotating assembly, and the benefits of increased engine vacuum are more pronounced in long-stroke, high-rpm motors that are more susceptible to parasitic horsepower loss due to windage.

In instances where engines are designed for use with a dry sump system from the ground up, they can be built with lower tension oil rings. “With a dry sump oiling system, since there isn’t nearly as much oil in the bottom end, the rings don’t have to scrape as much oil off the cylinder walls. This lets you get away with running half as much ring tension as in a wet sump engine without burning any oil, which dramatically reduces friction,” explains Erik Koenig of HKE. “In fact, with the heads removed you can turn over a race motor by hand with as little as 5 lb-ft of torque with low-tension rings, whereas a street/strip engine with standard tension rings might require 35 lb-ft. That 30 lb-ft–reduction in drag at high rpm equates to a big increase in horsepower. In an engine with a 1/16-, 1/16-, 3/16-inch ring package, the combination of a crankcase vacuum, improved ring seal, and low-tension rings can net a 30-40hp increase. Since the pressure in a dry sump system is adjustable, they also let you pump the minimum volume of oil necessary to lubricate the motor, which further reduces drag and parasitic power loss.”

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In race setups that utilize a separate vacuum pump, a dry sump oiling system allows cranking up the vacuum without fear of compromising oil flow. When a vacuum pump is bolted to an engine with a wet sump oiling system, it creates a tug-of-war in which increasing vacuum reduces oil pressure. That’s because there’s less air pressure inside the crankcase to help push oil through the oil pump. In many instances, trying to pull more than 16 inches of vacuum will negatively impact oil pressure. On the other hand, since a dry sump system stores oil in an external tank — where 14.7 psi of ambient air pressure is always pushing down on the oil regardless of crankcase vacuum — engine builders can pull as much vacuum as desired without adversely affecting oil pressure and potentially burning up the bearings. As Erik asserts, however, on a well-sorted engine combo, it isn’t always necessary to run both a dry sump oil pump and a vacuum pump. “If a motor is sealed up well with good pistons, rings and straight bores, you can make a lot of vacuum with just a dry sump pump,” he says. “With big power adder motors that get a lot of blow-by, you might run a vacuum pump in addition to dry sump oil pump. That said, with most all-out race motors, just having a dry sump oil system will generate enough vacuum to control oil flow and seal up the rings.”